Zielgruppe: Personen die an Angriffsszenarien gegen IoT-Geräte und eingebettete Systeme interessiert sind Schwerpunkt: technisch Sprache: Deutsch Abstract: ********** Dieser Vortrag gibt einen Einblick in physische Angriffe gegen IoT-Geräte und eingebettete Systeme. Mögliche Angriffe sowie Gegenmaßnahmen werden im Überblick präsentiert. About the Speaker: ********************* Christian Kudera is researcher and security analyst at SBA Research. Christian received an MSc in Hardware & Software Security from TU Wien. Currently he is working towards his PhD degree with the focus on Internet of Things and embedded systems security. He has more than six years of experience as security analyst in the areas of hardware and software security. He teaches multiple courses at TU Wien (Internet Security, Advanced Internet Security) and at Universities of Applied Sciences (Rosenheim Technical University of Applied Sciences, FH Campus Wien, FH St. Pölten).

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Welcome
to the SBA Live Academy
#bleibdaheim #remotelearning
Today: Physical Attacks against (I)IoT-Devices, Embedded
Devices, Microcontrollers and System on Chips (SoC)
by Christian Kudera
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Physical Attacks against (I)IoT-Devices,
Embedded Devices, Microcontrollers and
System on Chips (SoC)
Christian Kudera
SBA Research gGmbH, 2020

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Acknowledgement
• Presentation partially based on slides
from Markus Kammerstetter
(Trustworks GmbH)
o https://www.trustworks.at/
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Hardware Security
Fundamentals
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Newer Designs
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Integrated Circuit (IC): Die
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IC Structure

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Mechanical Invasiveness
• Non-invasive
o It is not necessary to open the chip
• Semi-invasive
o The chip has to be decapsulated, so that the die is visible
o Passivation layer stays intact
• Invasive
o The chip is fully decapsulated
o Passivation layer is (partially) removed
o Physical contact to chip signals possible
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Costs

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Hardware Security
Non-Invasive Attacks
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A bad password check
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bool check_password(char *passwd)
{
for (int i=0; i<pass_len; i++)
{
if (passwd[i] != stored_passwd[i])
return false;
}
return true;
}

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A bad password check
SBA Research gGmbH, 2020
bool check_password(char *passwd)
{
for (int i=0; i<pass_len; i++)
{
if (passwd[i] != stored_passwd[i])
return false;
}
return true;
}
Terminates as soon
a byte is wrong
Based on timing information, it’s is easy to guess the password

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A better password check
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bool check_password(char *passwd) {
int err=0;
for (int i=0; i<pass_len; i++)
{
err |= passwd[i] ^ stored_passwd[i];
}
if (err != 0)
return false;
return true;
}
Constant time

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Simple Power Analysis
• The power consumption of a processor depends on
the instruction executed
• Security analyst / attacker closely monitors the power
consumption during clock cycles (i.e. time domain)
• For a given instruction, the power consumption also
depends on the data processed
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Simple Power Analysis
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Vulnerable RSA exponentiation
• Example:
• Using SPA, it’s possible to completely recover the
RSA secret key during the exponentiation of large
integers!
SBA Research gGmbH, 2020
[Cryptography Research, Inc.]

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Side Channel Countermeasures
• Use secure components (e.g. microcontroller
with implemented countermeasures)
• Leakage reduction (e.g. through balancing)
• Noise introduction
• Masking (e.g. through insertion of random
dummy cycles)
• Obfuscation
SBA Research gGmbH, 2020

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Clock Glitching
• For a short time, the IC receives a clock pulse that is too
fast for the IC to fully process:
• Some of the IC operations will work as intended (e.g.
increase program counter), others will not finish and get
interrupted
• Can be used to skip code (e.g. conditional jump in
password check)
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Voltage Glitching
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Practical Example
• Bozzato, Claudio, Riccardo Focardi, and Francesco
Palmarini. "Shaping the Glitch: Optimizing Voltage Fault
Injection Attacks." IACR Transactions on Cryptographic
Hardware and Embedded Systems (2019)
• Firmware extraction via fault injection
o STMicroelectronics: STM32 F1, STM32 F3
o Texas Instruments: MSP430 F5xx
o Renesas Electronics: 78K family (e.g. 78K0/Kx2)
SBA Research gGmbH, 2020

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Fault Injection Countermeasures
• Use secure components (e.g. microcontroller
with implemented countermeasures)
• Environmental sensors
• Tamper sensors
• Internal filtering
• Shielding
SBA Research gGmbH, 2020

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Cold Boot Stepping
• Obermaier, Johannes, and Stefan Tatschner. "Shedding too
much light on a microcontroller's firmware protection."
11th USENIX Workshop on Offensive Technologies (WOOT
17). 2017
• Analysis of the STMicroelectronics STM32 F0 security
concept
SBA Research gGmbH, 2020

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Hardware Security
Semi-Invasive Attacks & Invasive Attacks
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Wet Chemical Decapsulation
• Epoxy package is very resistant
• Epoxy can be dissolved in
concentrated and heated up acids
(usually fuming HNO3, H2SO4 or
a combination thereof)
• Bonding wires, pads and passivation
layer stays intact, copper wires can be an issue
• Easy to conduct, but safety equipment necessary
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Wet Chemical Decapsulation
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1 – Carefully mill a cavity

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Wet Chemical Decapsulation
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2 – Carefully apply
nitric acid (HNO3) /
sulfuric acid (H2SO4) on
hot plate
Safety equipment &
fume hood

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Wet Chemical Decapsulation
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3 – Rinse in Acetone

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Wet Chemical Decapsulation
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4 – Repeat etch & rinse
until die fully exposed

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Wet Chemical Decapsulation
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5 – Clean in Acetone in
ultrasonic cleaner to
remove remaining
residue

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Wet Chemical Decapsulation
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6 – Chip ready for further
analysis and/or attack
Chip is still functional

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Optical Microscopy
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Scanning Electron Microscope
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Plasma Deprocessing
• Principle of plasma etching already
covered (i.e., plasma decapsulation)
• Advantage:
o Very clean results
o strong selectivity
o passivation removal
• Disadvantages:
o Metal etching requires highly toxic Chlorine based
gases
o Formation of “RIE grass”
SBA Research gGmbH, 2020

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Polishing
• Use slurry with silica crystals
for polishing
• Die is mounted with special wax
• Alignment is key to get planar polishing
results
• Disadvantage:
o Uneven results
o Material dependent
removal rates
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Example: Metal Layer Removal
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Top metal layer Below interconnect layer exposed

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Example: Via Imaging
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Automated Gate Recognition
• Using pattern recognition, security analyst / attacker can
identify the standard cells and how they are interconnected
• It’s possible to reconstruct the implemented logic
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Focused Ion Beam (FIB)
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Summary & Takeaway
• Physical attacks are a serious threat for the IoT
and embedded devices
o Know the risks and consider them in a threat
analysis
• Use secure components if necessary
o Be aware that an attacker may still be able to
extract the firmware or particular secrets
SBA Research gGmbH, 2020

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Christian Kudera
SBA Research gGmbH
Floragasse 7, 1040 Vienna
ckudera@sba-research.org
SBA Research gGmbH, 2019